Continuous chemical reactions

ABSTRACT

A CONTINUOUS CHEMICAL REACTION IS CARRIED OUT IN A CLOSED LOOP TUBULAR REACTOR. SPHERICAL SEPARATORS SPACED APART IN THE TUBE DIVIDE THE TUBE INTO CELLS. THE CELLS AND SEPARATORS ARE PROPELLED PAST FIXED STATIONS AT WHICH OPERATIONS ARE PREFORMED WHICH INFLUENCE THE CHEMICAL REACTION. THE REACTION PRODUCTS ARE DISCHARGED AT THE END OF THE TUBE, AND THE SEPARATORS ARE RECOVERED THROUGH A LOCK AND REINTRODUCED AT THE BEGINNING OF THE TUBE.

July 27, 1971 Filed April 29. 1968 G. ROUZIER 3,595,846

CONTINUOUS CHEMICAL REACTIONS 7 Sheets-Sheet 1 GEORGIES ROUZIER his ATTORNEYS July 27, 1971 G.=ROUZIER 3,595,846

CONTINUOUS CHEMICAL REACTIONS Filed April 29, 1968 '7 Sheets-Sheet 2 I N VIjN'I UR.

GEORGES ROUZIER N BY W, FM, A

hIS ATTORNEYS July 27, 1971 ROUZIER 3,595,846

7 CONTINUOUS CHEMICAL REACTIONS Filed April 29, 1968 '7' Sheets-Sheet 3 BY N W his ATTORNEYS July 27, 1971 s. ROUZIER CONTINUOUS CHEMICAL REACTIONS 7 Sheets-Sheet 4 Filed April 29 712 58 mckudmm m0 ZGEO wmmdIowa .m|

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GEORGES ROUZIER ATTORNEYS July 27, 1971 G. ROUZIER CONTINUOUS CHEMICAL REACTIONS 7 Sheets-Sheet I Filed April 29, 1968 INVIjA/IYJR.

GEORGES ROUZIER BY W, m) M A QML his ATTORNEYS July 27, 1971 e. ROUZIER 3,595,846

CONTINUOUS CHEMICAL REACTIONS Filed April 29, 1968 '7 Sheets-Sheet 6 FIG /0 ,A FIG. I!

4O 2O 40 2O K 35 I5 35 30 25 20 I5 GEORGES RO'UZIER BY BM Gal v 4 z his ATTORNEYS July 27, 1971 s. ROUZIER 3,595,846

CONTINUOUS CHEMICAL REACTIONS Filed April 29, 1968 '7 Sheets-$heet 7 F/G. I5

lNVLi'N/UR GEORGES ROUZI ER his ATTORNEYS 3,595,846 CONTINUOUS CHEMICAL REACTIONS Georges Rouzier, Clermont-Ferrand, France, assignor to Compagnie des Etablissements Michelin raison sociale Michelin & Cie, Clermont-Ferrand, France Filed Apr. 29, 1968, Ser. No. 725,102 Int. Cl. C08f 3/68, 1/98; C08d 1/00 US. Cl. 260--89.5 Claims ABSTRACT OF THE DISCLOSURE A continuous chemical reaction is carried out in a closed loop tubular reactor. Spherical separators spaced apart in the tube divide the tube into cells. The cells and separators are propelled past fixed stations at which operations are preformed which influence the chemical reaction. The reaction products are discharged at the end of the tube, and the separators are recovered through a lock and reintroduced at the beginning of the tube.

BACKGROUND OF THE INVENTION The present invention relates to chemical reactions and, more particularly, to novel and highly-effective methods and apparatus facilitating continuous chemical reactions, particularly polymerizations or copolymerizations of olefins or diolefins. The invention relates also to the products, especially the polymers and copolymers, obtained in accordance with the invention.

Industrial chemical reactions are most frequently carried out in reactors operating continuously and under steady-state conditions. The reactor system is said to be of the continuous or open type. Several reactors of this kind can be operated simultaneously, the reactors being connected in parallel, in series, or in a more complex way.

This manner of operation differs from that customarily used in laboratories or wherever small quantities of products are manufactured. Laboratories use essentially discontinuous or closed-type reactors, which do not permit contact of reacting materials in the reactor with the outside in the course of the reaction. They also use reactors of the half-closed type, which facilitate only intermittent or episodic exchanges of the reactor contents with the outside. Chemical reactions in closed and half-closed reactors are carried out under transitional rather than steady-state conditions, and the concentrations of materials within the reactors vary constantly.

Open reactors operating continuously are preferred by industry, since their operation is less complicated, more economical, and better adapted for automation. However, their possibilities are more limited than those of closed or half-closed type reactors, inasmuch as the latter enable the operator to interfere at any time and to control the chemical reaction as he desires. Conditions including speed, temperature, pressure, and concentration can be changed at will; new reagents can be introduced; and all or part of the reaction products can be drawn off. It is thus possible to take into account reactional selectivity, critical operations, and the kinetics of reactions and thus to obtain an optimal progression of the desired chemical transformation. These capabilities are of particular importance in the case of complex reactions. In contrast, interference by a chemist is not possible in case of a single conventional open reactor and barely possible in the case of multiples of open reactors. Since the cost of installation grows rapidly as the number of reactors used increases, even this limited ability to exert closer control over complex reactions using open reactors is purchased at a high price.

The close control of one kind of reaction of industrial United States Patent 0 3,595,846 Patented July 27, 1971 importance is of special interest. It is polymerizations or similar reactions, such as polycondensations and polyadditions, where modification of the reaction is tantamount to the modification of the product itself and to its gradual build-up by following a pro-established evolution or program. Thus, the conduct of the reaction makes it possible to influence the structure of the product.

SUMMARY OF THE INVENTION An object of the present invention is to combine the simplicity and economy of continuous or open reactors with the flexibility and variability of the closed or semiclosed type. Another object of the invention is to facilitate the industrial manufacture of products which can be manufactured today only in the laboratory, under conditions of reproducibility and regularity difficult to obtain in the laboratory. A further object of the invention is to facilitate the manufacture of large quantities of products, especially polymers and copolymers, conforming to predetermined specifications and under conditions of automation equalling those characterizing the classical continuous methods.

The foregoing and other objects of the invention are attained, in a representative method in accordance with the invention for continuously carrying .out chemical reactions, especially polymerizations and copolymerizations particularly of olefins or diolefins, by acting on separate measured quantities of reacting materials contained in cells movable within a fixed tube, the cells being separated from one another by movable separators. The method is characterized in that the cells are caused to circulate sequentially past a plurality of spaced-apart stations where the transported measured quantities are continuously acted on by means of programmed operations such as injection of products (solvents, reagents, catalysts, etc.), drawing off or recycling of products, modification of the operating conditions (especially the temperature), mixing, taking of samples, and measurement of parameters. Towards such end, the cells, always full, have a variable volume because of the moving apart or closer together of the separators. Moreover, the range of times within which the various operations are carried out is a function of the distance of the several stations from a point of origin.

The method in accordance with the invention thus combines the advantages of the continuous method with those of the discontinuous method. Each cell is in effect a small reactor of the closed or semi-closed type. The cells circulate continuously along a circuit through which they travel sequentially: i.e., one after another. At each station of the circuit, steady-state conditions prevail. On the other hand, in each cell, conditions are transient or changing all along the circuit.

Tubular reactors for conducting continuous reactions are already known. However, in these conventional reactors, one does not undertake a modification of the reaction or act upon separate and discontinuous quantities of the reacting materials. Consequently, the results obtained are greatly different.

Likewise, it has been suggested that there be carried out in tubular reactors reactions with measured quantities of products separated from one another by movable separators. However, this suggestion provides only for obtaining piston discharge without organization of the evolution of the reaction within each measured quantity, by interventions which take place continuously in order to influence the nature or the qualities of the product obtained.

In accordance with the method of the invention the reacting materials are preferably mixed at least in part prior to entering the reactor, and the reaction is then 3 carried out in the reactor proper. In order to achieve start-up, it is advisable to introduce into the reactor only preliminary mixtures or reagents which until then are inert.

In one embodiment of the invention, it is possible to modify cyclically the conditions of intervention at the various intervening stations, in order to produce simultaneously several different products intended for mixing.

Thus, the concentration of a catalyst or one or another reagent may be varied in accordance with a certain rule, in order to obtain in succeeding cells polymers having different characteristics-for example, different average molecular weights. Successive cells can be periodically specialized for the production of a given polymer in different molecular weights, in order to obtain by mixing a batch of a polymer having a molecular weight distribution with a desired profile.

Similar effects may be obtained by a recycling of fractions of the reaction medium, possibly combined with a short-'circuiting of other fractions of the reaction medium, so as to obtain a wider range of ages of the macromolecules produced. Likewise, and especially in anionic polymerizations, one may vary the distribution of the molecular weights by injecting at selected stations a catalyst or a stopper.

The method in accordance with the invention is applicable in particular to the polymerization or copolymerization of monomers, especially unsaturated monomers, such as ethylene, propylene, butylene, butadiene, isoprene, styrene, and methyl methacrylate, as well as all their higher homologs and many of their derivatives including their halogen derivatives.

Of course, the various classical reaction methods can be used, such as polymerization in bulk, in solution, in suspension, and in emulsion. Also conventional catalytic and initiator methods can be used. However, it is preferable to work in a liquid stage and that reagents or monomers in gaseous condition be dissolved in a solvent or liquefied under pressure. It is possible to operate within a wide range of temperatures and pressures, especially to have a temperature profile which is variable in the course of the reaction in each cell or compartment of the reactor. Generally, profiles of pressure decrease from one end to the other of the reactor and thus from the start to the end of the reaction.

The method in accordance with the invention can be practiced by means of any suitable apparatus. Preferably however, it is practiced by using a reactor the design of which forms part of the present invention.

The reactor in accordance with the invention comprises a tube of substantially constant cross-sectional shape and interior surface, wherein the reaction medium is caused to circulate in distinct doses partitioned off by movable separators, preferably of spherical shape. The tube forms a closed circuit between a point of origin and a terminal point, which points are separated by a partition which is impervious to the reaction medium and traversed by agate or lock facilitating the transfer of the separators from the terminal point to the point of origin, so that the separators are recycled. Between the point of origin and the terminal point, a permanent pressure differential is established by any suitable means sufficient to keep the tube full and to assure the propulsion of the reaction medium and the separators, both substantially at equal speed, in relation to the tube, such speed preferably remaining invariable at any given point of the circuit.

In a tube in which fluid flow is laminar, the difference in pressure between two points, for example the tube intake and discharge, is a function of the delivery rate and the viscosity of the fluid. In accordance with the invention, the difference in pressure between the point of origin and the terminal point should be such that the speed of the fluid exceeds the minimum value starting at which the separators are carried along at the same speed as the fluid, so that lil the effective tightness between the separators and the wall of the tube is maintained even if a considerable clearance exists. Such minimum value depends on the viscosity of the fluid, the shape and the size of the clearance between separators and the inner wall of the tube, and the ascending or descending slope of the tube.

The difference in pressure to be established between the point of origin and the terminal point may be obtained by means of pumps which inject fluids constituting the reaction medium at the point of origin and at intermediate points and by means of a discharge valve the delivery rate of which can be regulated. In place of pumps, one can also use hydrostatic pressure supplied by reservoirs placed at a higher level than the tube. Preferably, the discharge valve is regulated in relation to the intake pressure of the tubular reactor so as to maintain the pressure differential constant and to stabilize the pressures and rates of flow at all points of the reactor, thereby facilitating the establishment of a steady-state flow at each point.

By stabilizing the delivery rates and speeds, one renders uniform the dwell of the reaction medium in the tube, subjects all parts of the reaction medium to the same evolutionary cycle, and thereby obtains a uniform reaction product.

Preferably, the circuit formed by the tube is designed in such a manner as to spread the load losses and the progressive drop of pressure over a great length in relation to the diameter of the tube, so that on either side of each separator and in the vicinity of it the pressures can be considered as practically equal.

Preferably also, the tubular reactor is constructed of tubular elements which are arranged almost horizontally, and the separators have a density which is close to that of the reaction medium. The urpose of this provision is to avoid subjecting the separators and the reaction fluid to different effects of gravity. A too-steep incline of the tube may cause the separators to move through the tube at a speed different from the speed of the reaction fluid. However, it is possible to provide for a difference in levels of the ends of the tube in the vicinity of the points of origin and discharge so as quickly to communicate to the separators collected at the discharge end the speed of circulation of the fluid into which they are introduced at the origin. The rectilinear elements of the tube can be mounted to ascend at a shallow angle, whereby a more pronounced descending inclination can be given the curved elements connecting the rectilinear elements. This facilitates the passage of the separators through these curved elements. However, a difference in levels or substantial inclinations between points near each other requires in general a compensation in form of a reduction of the clearance between the separators and the inner wall of the tube, especially if the reaction medium has a low viscosity. This is true, for example, in the vicinity of the terminal point, where the tube preferably rises again to its initial level, if the final viscosity at the end of the reaction has not substantially increased.

In one embodiment of the invention, the tubular reactor consists of a bundle of tubular elements which are rectilinear and have the same length and are arranged almost horizontally and in parallel in superimposed layers at slightly different levels and are connected by semicircular knees. Each tube is enclosed in a second cover which is heat-insulated and wherein a fluid serving for heating or cooling is circulated. The various injections or interventions preferably take place in the connecting knees.

The separators have preferably a spherical shape, which enables them to roll in the tube. There is,of course, less friction for separators that roll than for those that slide. Furthermore, this facilitates passage with minimum clearance through the semicircular knees. Their density is close to the density of the reaction medium so as to render their floatability as low as possible and to eliminate zones of local contact or impact at the wall of the tube. Towards such end, one may make use of hollow spheres obtained, for example, by a welding or soldering together of hemispheres made of metal of some suitable thickness. The separators can consist of any material that is chemically inert in the reaction medium. Of course, a form other than spherical may be provided without exceeding the scope of the invention: for example, a cylindrical shape which bulges out in the middle or which is provided with sealing elements such as the sealing rings of the pistons of internal combustion engines.

The clearance between the separators and the inner wall of the tube-i.e., the difference between the radii of their cross sections-is preferably, but not necessarily, small: for exampe, ranging around one or two percent of the inner diameter of the tube. Absolute tightness is not required. The relative tightness must increase as the inclination of the tube with respect to the horizontal increases and as the speed of the reaction fluid decreases. Experience has shown that for each combination of a given clearance between the separators and the inner Wall of the tube, a give viscosity of the fluid, and a given incination of the tube, there is a minimum speed of the fluid starting with which the relative speed of the separators with respect to the fluid becomes substantially zero. For example, for a horizontal tube carrying a liquid having the viscosity of water and spherical separators the diameter of which is 99% of the inner diameter of the tube, the minimum speed is about 1 to cm./sec. for tube diameters ranging from to 500 mm. In practice, it is advisable to use a substantially higher circulation speed, in order to be far enough above the critical speed to avoid slippage between separators and fluid in case of accidental speed reduction. In general, speeds ranging from 1 to 10 times the diameter of the tube per second are suitable, especially if the clearance between the inner wall of the tube and the separators is approximately 1 to 2 hundredths of the inner diameter of the tube.

The distance between consecutive separators and thus the total number of separators present simultaneously can be varied within a Wide range. Although the invention comprises the case in which the reactor is divided into only two or a small number of compartments, it is preferable to use a large number of compartments and of separators without, however, a reduction of the length of each compartment to less than 10 times the diameter of the tube. In general, good results are obtained with compartments the length of which ranges from 10 to 200 times the diameter of the tube.

In one embodiment of the invention, the connection between the terminal point of the tubular reactor and the point of origin is effected by a distributor assembly comprising a tight partition through which fluid cannot pass but which the separators can traverse by means of a lock or gate. The interior volume of the lock is substantially the same as that of a separator so that substantially no reaction fluid is carried along.

Various devices can be used to enable the separators to clear the tight partition. For example, there may be provided two coaxial cylinders capable of sliding in a tight manner across the partition, each cylinder having in one of its bases a cavity corresponding to half the volume of a separator. By means of translational motions, these two cylinders can seize a separator on one side of the tight partition, carry it to the other side, and discharge it there. Hydraulic jacks or any other suitable means effect the translational movements of one or both of the cylinders.

Another, preferred, system consists in the application of at least one of the two cylinders with its hollow base against the tight wall which has an opening the dimensions of which permit the passing of one separator. In this manner, the two cylinders secure alternatingly the tight closing and the opening for passing of the separator.

Of course, it is possible to use several gates in series or in parallel, and, in particular, to undertake, between the extraction of a separator from the circuit by means of one gate and its reintroduction, various operations, such as, for example, rinsing of the separator to eliminate any traces of the reacted product that may be carried along, or, also, its replacement.

The reactor in accordance with the invention affords great ease of control of operations. For example, by automatic measurement in certain points of the parameters, such as temperature or concentrations, it becomes possible to cause, upstream or downstream, an increase or decrease of the flow, for example, of the thermal flux, or also of the rate of injection of a reagent.

BRIEF DESCRIPTION OF THE DRAWING An understanding of additional aspects of the invention may be gained from a consideration of the following detailed description of several representative embodiments thereof and of the accompanying figures of the drawing, in which:

FIG. 1 is a plan view of a simplified embodiment of a reactor in accordance with the invention;

FIG. 2 is a perspective view, partly schematic, of a preferred embodiment of a reactor in accordance with the invention;

FIG. 3 is a cross sectional view in the plane 3-3 of FIG. 2, the view being in the direction indicated by the arrows;

FIG. 4 is a longitudinal section. of a portion of the apparatus of FIG. 2;

FIG. 5 is a longitudinal section of another portion of the apparatus of FIG. 2;

FIG. 6 is a detailed plan view of a portion of the apparatus of FIG. 2 shown schematically in FIG. 2;

FIG. 7 is a sectional view in the plane 77 of FIG. 6, the view being in the direction indicated by the arrows;

FIG. 8 is a sectional view in the plane 8-8 of FIG. 7, the view being in the direction indicated by the arrows;

FIG. 9 is a sectional view in the plane 9-9 of FIG. 7, the view being in the direction indicated by the arrows;

FIGS. 10 to 15 are graphs showing certain important characteristics of polymers respectively obtained in the case of Examples 1 to 6 which follow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates somewhat diagrammatically the reactor and the method in accordance with the invention as applied, for example, to a copolymerization of styrene and butadiene dissolved in heptane, by means of a catalyst of the butyl lithium kind.

A tubular chamber 21 is connected at a point of origin 22 and a terminal point 23 to a distributor 24 including lock means. The tubular chamber 21 contains a reaction medium divided into doses 25 by means of spherical separators or balls 26.

The tube 21 is surrounded by double covers 27 each having an intake 28 and an outflow 29 making it possible to circulate around the tube 21 a fluid regulating the temperature of the reaction medium contained in the tube 21. The division into sections of the double covers 27 makes it possible to maintain different temperatures of the reaction medium at various points along its travel. A certain number of intervening stations is provided along the route and the interventions take place continuously.

The distributor 24 is connected to an intake 31 for fluid under pressure which may consist, for example, of the solvent containing the monomers. The pressure is generated by a pump P in the intake 31. At the first intervening station 32 the catalyst is introduced by means of a metering pump 33.

At a second intervening station 32, the mixing takes place. The reaction medium is drawn from the tube 21 through a tube 34 and forced back through a tube 35 by means of a pump 36. At the same time, supplementary injection is provided at a point 38 by means of a pump 39 introducing, for example, a catalyst or one of the monomers.

At a third intervening station 40, part of the reaction medium drawn off through a line 41 by means of a pump 42 is recycled.

At a fourth intervening station 43, substance is drawn off by means of a pump 44 for the purpose of control, for example, of the proportion of styrene polymerized.

Naturally, the reaction can be slowed down or speeded up by reducing or increasing the temperature between sections ofthe tube, so that each of the jackets 27 constitutes an additional means for intervening in the process.

Finally, the reaction medium is discharged through line 45 which is in communication With the terminal point 23. This line 45 contains a variable discharge valve V regulated by a pressure sensor S which is connected to the valve V and which senses the pressure of the reaction medium near the origin.

The several spherical separators 26 are carried along by the circulating reaction medium, and the separation between adjacent separators 26 increases when materials for reaction are added and decreases when substance is drawn off.

The diameter of the balls 26 is substantially the same as the diameter of the tube 21. However, adjacent to the terminal point 23, the diameter of the tube 21 increases starting at a point 46. From there on, the tube forms a storage room for separators so as not to increase the loss of head due to the accumulation of separators.

The distributor 24 comprises a block traversed by a longitudinal bore 47 in which slide two pistons 48 and 49. The bore 47 is in communication with the intake 31 and the point of origin 22 on the one hand and with the discharge 45 and the terminal point 23 of the tubular chamber 21 on the other. The bore 47 is closed off in the middle by a tight partition 50 formed with a hole 51 the diameter of which is substantially equal to the diameter of the separators 26. The bases of the pistons 48 and 49 are formed with cavities 52 and 53, respectively, which are substantially hemispherical and have a diameter substantially equal to the diameter of the separator 26. The cavities 52 and 53 are surrounded by shoulders 54 and 55, respectively, adapted tightly to engage opposite sides of the partition 50. The pistons 48 and 49 are provided with ejectors 56 and 57, respectively, biased by springs 58 and 59, respectively, for the purpose of ejection of the balls 26 as described below.

Each of the pistons 48 and 49 is able to slide in the bore 57. Their movement is controlled, for example, by hydraulic jacks (not shown).

Whenever the piston 48 is forced against the partition 50, it prevents communication through the distributor 24 between the origin 22 and terminus 23 of the tube 21. When the piston "48 is sufliciently removed from the partition 50, a separator 26, carried along by the current, enters the bore 47. When the piston 49 is about to be placed against the partition 50, it seizes the separator 26, taking along practically no liquid, and, as soon as it is forced against the partition 50, it in turn prevents communication through the distributor 24 between the points 22 and 23. The piston 48 can move away now whereby the separator 26 is set free and carried along with the current. Seals 60 and 61 enable the pistons 48 and 49 to slide tightly in the bore 47. The transfer of a separator 26 from the terminal point 23 to the point of origin 22 is controlled manually, or automatically by any suitable means including an automatic switch S operated at timed intervals or by the passage of a separator through a given point of the circuit, e.g., the point 46.

FIGS. 2 to show a'preferred embodiment of a reactor in accordance with the invention.

The reactor comprisse a tube assembly formed by a series of straight or rectilinear segments 70. Each tube 70 is surrounded by a double envelope 71 (FIG. 4) provided with an intake 72 and discharge 73 for the heating or cooling fluid. At each end there is installed a fixed flange 74 and a movable flange 75. Two successive straight tubes 70 are connected by a U-shaped segment or knee 80, the latter being formed with two fixed flanges 81 which are bolted to the movable flanges 75. In the flanges 81 there are provided threaded bores 82 into which are screwed either a stopper or a connection to a line and pump for injection or drawing off.

As FIG. 3 shows, the tubes 70 are not on the same level in each layer. A slight upward slope is provided, for example 1%, in the direction of circulation so that the knees are at dilferent levels at each end. The knees 80 are shorter than the straight segments 70, and their slopes, which are downward, are correspondingly steeper. This facilitates the passing of the balls 26 through the knees 80. To this end, it is sufiicient to mount the tubes 70 on supports 85 by means of wedges 86 placed at the downstream end of each tube.

FIG. 2 shows the point of origin 22, the terminal point 23, the distributor 24, the main fluid intake 31, and the discharge 45. The last tube 87 is the only one which shows a consideable incline and which requires inside machining with great precision so that the clearance between the inner wall and the separators is small, in order for the separators to be carried along notwithstanding the ascending slope. However, if the viscosity of the reaction medium is sufficiently high at the end of the reaction, or if thevelocity through the tube is sufliciently great or the straight sections of the tube are sufliciently long, the separators move with the fluid through the ascending slope even in the absence of precise machining.

FIG. 2 also shows the feed 32 of additional fluid as well as a point of intermediate injection 35.

FIGS. 6 to 9 illustrate a distributor comprising lock means which has been operated with excellent results in combination with a tubular chamber such as the one shown in FIGS. 2 to 5.

The distributor comprises a block formed with various transverse andlongitudinal bores and one vertical bore.

Superimposed transverse bores 121 and 122 serve for the passage of fluids constituting the reaction medium, the bore 122 communicating with the reaction tube at the point of origin 22 and the bore 121 communicating with the reaction tube at the terminal point 123. The role of the distributor is to permit the transfer of the balls from the bore 121 to the bore 122 through lock means which prevents the passage of fluid.

The upper bore 121 is connected to a tube 123 forming the end of the tubular reactor and to a tube 124 constituting the discharge for the fluids and connected to the discharge valve (not shown).

' The lower bore 122 is connected to a tube 124 forming the feed 31 of'the reactor and to a tube 125 forming the start of the tubular reactor.

The distributor comprises furthermore two longitudinal bores and 131 (FIG. 7) which are superimposed and run into the transverse bores 121 and 122, respectively, at right angles. In the bores slide pistons 133, 134, and 135, 136, respectively. There are securely mounted in the bores 130 and 131, at the junction of the bores 121 and 130 and at the junction of the bores 122 and 131 cylindrical screens 137 and 138, respectively, which permit passage of fluids but prevent passage of the balls 139 and 140 in the bores 121 and 122, respectively.

Inflatable seals 141 held by rings and connected to intakes of fluids under presure facilitate the sliding of the pistons While preventing leakage of fluid.

The two pistons 133 and 135 on the one hand and 134 and 136 on the other are connected to flanges and 151, respectively, by bolts 152, and the flanges 150 and 151 themselves are connected to rods 153 and 154 of hydraulic jacks 155 and 156, respectively. The pistons 133 and 134 have their bases facing each other, and each of the bases has a hemispherical cavity 157 with a diameter which is substantially equal to the diameter of a separator so that, Whenever a separator 139 is held between the two pistons, a minimum quantity of liquid is enclosed in the cavity together with the separator. Each of the pistons 133 and 134 is likewise equipped with an ejection system comprising an ejector 158, a spring 159, and a screw 160 which is threaded into a center thread 161.

The distributor has a vertical bore 170 connecting the bores 130 and 13 1. The bore 170 is connected to an intake tube 171 for separator washing fluid and to a tube 172 for discharge of the washing fluid. The tube 172 opens into an intermediate socket 173 closed off by a stopper 174 from which extends a center rod 175 the vertical position of which is adjustable by means of a wheel 176.

FIG. 9 shows a transverse bore 180 closed off by two glass plates 181 and 182 respectively mounted in frames 183 and 184 screwed to the block 120. The glass plates 181 and 182 make it possible to observe what goes on in the vertical tube 170.

The assembly of the fixed elements constituting the distributor, including the block 120 and the jacks 155 and 156, is mounted on a fixed frame 162 consisting of angle irons which are assembled by any suitable means including bolts, rivets, welding, and soldering.

The functioning of the distributor is easily understood. As FIG. 8 shows, the fluids kept in the reactor arrive at the distributor and travel through it by means of the tube 123, the bore 121 and the tube 124. However, the separators are stopped by the screen 137. To transfer a separator stopped by the screen 137 in the upper bore 121 to the lower bore 122, one operates the hydraulic jacks 155 and 156 (FIG. 7) to cause the pistons 133 and 134- to approach each other, whereby the spherical separator is seized by them. Thereafter, one causes their displacement in a manner whereby the separator is moved to the vertical bore 170. The separator is released by the jacks 155 and 156 and drops into the bore 170, being then driven by the washing fluid circulating in the tubes 171 and 172. The separator is stopped by the rod 175 and seized by the pistons 135 and 136. A displacing movement then guides the separator to the bore 122 (FIG. 8). whence it is carried by the fluid circulating in the tubes 124 and 125.

Experience has shown that a tubular reactor such as the one described in FIGS. 2 to 9 functions with outstanding results and can be easily adapted to various polymerizations and reactions. For best results, it is desirable that certain precautionary measures be taken during the start of operations. Thus, it is not advisable to start the apparatus and the system of distribution of the separators with an inert fluid, for example a pure solvent or a solvent containing monomers. Regulating becomes much easier if the reaction is initiated first, whereafter the distribution of the separators can be started. In the latter case, one obtains from the start a first approximation of what the viscosity of the reaction medium should be all along the tube. In the former case, i.e., with an inert medium, the viscosity may be much different from the viscosity of the medium in the process of reaction.

The purpose of the following examples is to demonstrate what can be achieved by means of the method and apparatus in accordance with the invention. They have been carried out by means of a pilot reactor of the type shown in the figures and having the following numerical characteristics total volume of the tubular reactor: 90 liters inner diameter of the tubes: 24 mm.

length of individual tubes: 6 m.

total length of the tubular reactor: 200 m.

diameter of the spherical separators: 23.8 mm.

average spacing between separators: 1 In.

total rate of flow: approximately 45 liters per hour; i.e., a

dwell of 2 hours in the tubular reactor intake pressure: 8 to 10 kg./cm. depending on the tests intake and discharge pressure difference: 3.5 to 4 kg./cm.

for a liquid of 10 poises average viscosity temperature: variable along the chamber linear speed: 2.7 cm./sec.

EXAMPLE 1 At the intake of a reactor one introduces, under a pressure of 10 kg./cm. 40 liters/hour of heptane and 4.6 liters/hour of butadiene.

There is likewise introduced a few meters from the intake some butyl lithium at a rate of 0.055 p.p.h. (l p.p.h. is defined as 1 part by weight of the substance added per parts by weight of monomer). Mixing is effected by means of a pump withdrawing liquid from the tube and forcing it back into the tube through a short loop. The pump has a delivery rate which is much higher than that of the reactor. The temperature is maintained at 50 C. over the entire length of the reactor. The polymer solution obtained is antioxidized and stopped near the downstream end of the reactor. The conversion obtained is close to 100% and the resulting polybutadiene has an inherent viscosity of 2.35 with a Mooney plasticity of 50. Its polymeric structure is as follows:

The molecular distribution is shown in FIG. 10, graph A. For the purpose of comparison, graph B shows the molecular distribution of the polymers obtained under conditions as nearly as possible the same in the laboratory in flasks of 250 cm. and graphs C and D show the molecular distributions of polymers obtained by continuous reactions in a vat using the same catalytic system and substantially the same average reaction times and doses.

As may be seen, the polymer obtained in accordance with the method of the invention, even though prepared continuously, is similar to a pollymer prepared discontinuously in the laboratory. The standard deviation of the molecular weights is even slightly less.

EXAMPLE 2 One proceeds as in Example 1. However, in place of 4.6 liters/hour of butadiene, one uses 4.6 liters/hour of a mixture of 23% styrene with 77% butadiene. At the time the butyl lithium is added at a rate of 0.04 p.p.h., one introduces 0.10 p.p.h. of hexamethyl phosphorotriamide and mixes by suction and then forcing back at accelerated speed through a small loop by means of a centrifugal pump. The pressure at intake is 8 kg./cm. and the temperature is 30 C. all along the circuit. The resulting solution, which is antioxidized and arrested, is recovered at the discharge.

In this example, too, conversion is close to 100%. The inherent viscosity is 1.65, and the Mooney plasticity of the polymer is 48. The polymeric structure is as follows:

Percent 1-2 50 Trans 1-4 35 Cis 1-4 l5 Graph A (FIG. 11) shows the molecular distribution of the polymer obtained. Graphs B and C respectively, show the molecular distributions of the polymers obtained in a similar manner but with, respectively, 30% and 18% of styrene in the styrene-butadiene mixture in place of 23 Graph D shows the molecular distribution obtained when the separators are eliminated from the reactor, and graph E shows the molecular distribution obtained under the same conditions by means of a conventional open reactor.

1 1 EXAMPLE 3 The preceding example is repeated, except that the catalyst and hexamethyl phosphorotriamide (HMPT) are added in two batches. During the first stage, one introduces 0.013 p.p.h. butyl lithium and 0.036 p.p.h. HMPT and maintains a temperature of 35 C.

In a second stage, when conversion has attained 48%, i.e., substantially at a distance from the point of origin of of the length of the tubular reactor, one introduces 0.045 p.p.h. of butyl lithium and 0.08 p.p.h. HMPT in relation to the initial quantity of monomer and reduces the temperature to C.

The polymer obtained has a bi-dispersed molecular distribution shown in the graph A in FIG. 12. The characteristics are:

Rate of conversion "percent" 100 Inherent viscosity 2 Mooney plasticity 60 The copolymer obtained, while having characteristics similar to those of Example 2, offers the advantage of being easier to work.

EXAMPLE 4 One proceeds as in Examples 2 and 3 but using 3 injections of catalyst:

The first injection is at 0% conversion, i.e., in the vicinity of the origin, and consists of 0.012 p.p.h. butyl lithium and 0.036 p.p.h. HMPT.

The second injection is at 44% conversion, i.e., at a distance from the origin corresponding to 20% of the length of the reactor, and consists of 0.015 p.p.h. butyl lithium and 0.045 p.p.h. HMPT calculated on the basis of initial monomer.

The third injection is at 60% conversion, i.e., at a distance from the origin corresponding to 33% of the length of the reactor, and consists of 0.028 p.p.h. butyl lithium and 0.08 p.p.h. HMPT, calculated on the basis of the initial monomer.

The dwelling time is two hours, as in the other examples. The pressure at the intake is 8 kg./cm. The temperature is 35 C. between the first and the second injections, 27 C. between the second and the third injections, and 30 C. between the third injection and the point of introduction of the antioxidant and the reaction arrester.

The final polymer obtained, with a rate of conversion very close to 100%, has an inherent viscosity of 2.15 and a Mooney plasticity of 60. Its molecular distribution is a little wider than that of the polymer in Example 3, as shown in the graph A in FIG. 13. Although the Mooney plasticity is the same as in Example 3, the inherent viscosity is higher. One can thus at will prepare polymers with the same plasticity but with higher inherent viscosities than the ones prepared by the conventional methods or polymers with the same inherent viscosity but greater plasticity, i.e., a lower Mooney index of plasticity.

EXAMPLE 5 In this example, there is obtained a butadiene-styrene copolymer with a statistical distribution of the two monomers in the chains, without using a polar compound, such as tetrahydrofurane or hexamethyl phosphorotriamide.

At the head of the circuit one feeds in liters/ hour of heptane, 0.735 liter/hour of styrene, and 0.960 liter/hour of butadiene. Thereafter, one introduces lithium butyl in a quantity of 0.045 p.p.h. of the total of the monomers (4.6 liters/hour). The pressure at the start is 8 kg./cm. and the temperature is maintained at 60 C. all along the circuit. The styrene part of the copolymer is controlled in a manner whereby the percentage of styrene in the polymer which is formed does not exceed 55%. To this end, one introduces a supplementary quantity of butadiene. Thus, one adds, successively, 0.6 liter/hour; 0.48 liter/hour;

0.375 liter/hour; 0.285 liter/hour; 0.235 liter/hour; and 0.185 liter/ hour of butadiene at points located, respectively, at distances of one-, tWo-, three-, four-, five-, and sixsevenths of the length of the reactor from the point of entry.

As a result of these six additions of butadiene, the average composition of the copolymer is 22% styrene, the content of 1-2 structures is approximately 10%, and the conversion of the styrene monomer is The polymerization may be continued by further additions in several stages of butadiene. In such case, the 12 content remains close to 10%.

One may also add the remaining butadiene at once, i.e., at a rate of 0.775 liter/hour as Well as 0.10 p.p.h. HMPT (calculated on the basis of the total monomer quantity). In such a case, one avoids the formation of a styrene block, and the macromolecules end in a statistical sequence of the two monomers with 22% of styrene. In the latter case, the polymer obtained has an inherent viscosity of 1.9, a Mooney plasticity of 50, and a 1-2 content of 18%. The profile of the styrene compositions at any given time appears in the graph A in FIG. 14, which shows the styrene percentage of the polymer formed at successive points along the reaction tube as a function of the percentage of conversion of the styrene monomer.

EXAMPLE 6 In this example, it is the aim to influence, on the one hand, the distribution of the'monomers (butadiene and styrene) in the chains, and, on the other, the microstructure, especially the 1-2 content, as indicated in a French Pat. No. 1,519,743 of Feb. 20, 1967, of Socit Michelin & Cie.

One introduces into the reactor, under a pressure of 10 kg./cm. an hourly flow of 40 liters of heptane, 0.75 liter of styrene, and 2.66 liters of butadiene.

One also adds 0.035 p.p.h. butyl lithium and 0.025 p.p.h. HMPT, calculated on the total rate of monomer (4.6 liters).

The temperature is maintained along the entire length of the tube at 60 C.

Inasmuch as the HMPT quantity is insufficient for obtaining a complex with the butyl lithium, the copolymer which forms is not completely statistical and becomes enriched in styrene but has a low 12 content.

At a point removed from the origin a distance along the tube equal to /s of the length of the tube, the butadiene complement is introduced at an hourly rate of 1.28 liters. As the composition of the monomers is moditied, the composition at successive points along the tube of the copolymer which is formed becomes progressively richer in butadiene.

At a point removed from the origin a distance along the tube equal to A; of the length of the tube, one introduces 0.050 p.p.h. of HMPT calculated on the basis of the total monomer quantity.

The profile of the instantaneous compositions of the copolymers (proportion of styrene) is indicated in the graphs in FIG. 15 in the same manner as in FIG. 14. The full line A plots the instantaneous styrene content, and the broken line B the mean styrene content of the copolymer formed.

The copolymer obtained has the following characteristics: inherent viscosity: 1.70; Mooney plasticity: 57; 1-2 content: 29%; trans 1-4 content: 47%; vitreous transition temperature during diiferential thermal analysis: 54 C.

The graphs indicate:

(a) as regards Examples 1 to 4, the molecular distribution, measured by means of the gel permeation chromatography method;

(b) as regards Examples 5 and 6, the percentage of styrene fixed in the copolymer obtained by measurement of the refraction index as a function of the rate of conversion of the monomers (total quantities).

Thus there are provided in accordance with the invention novel and highly-effective methods and apparatus making it possible to obtain continuously, with much greater ease than by conventional means, the close control of polymerizations and the polymers resulting therefrom.

Many modifications within the spirit and scope of the invention of the representative embodiments thereof disclosed above will readily occur to those skilled in the art. Accordingly, the invention is to be construed as extending to all the modifications thereof within the scope of the appended claims.

I claim:

1. A method of carrying out polymerization or copolymerization reactions comprising the steps of continuously introducing solvent, monomer and catalyst material for reaction into a tubular reactor at a point of origin, said monomer being selected from the group consisting of olefins, diolefins, styrene, methyl methacrylate, and halogenated derivatives thereof, introducing at intervals of time at said point of origin spaced separators to divide said material into discrete batches, setting up a plurality of stations along the length of said tubular reactor, propelling said separators and batches through said tubular reactor and past said stations to a terminal point of said tubular reactor, changing the polymerization or copolymerization conditions at at least one of said stations in at least one of the following ways: (a) introducing more of the same kinds of solvent, monomer or catalyst material, (b) introducing other kinds of solvent, monomer or catalyst material, extracting a portion of said material, and (d) changing the temperature of said material, each change in the volume of said batches being accompanied by a corresponding change in the spacing of said separators, the distance of said one station from said point of origin depending at least in part on the time elapsed from the start of the reaction and on the flow speed of said material, whereby a polymer or copolymer is produced in said batches successively, discharging said polymer or copolymer from said tubular reactor at said terminal point, and recovering said solvent and separators for recycling with fresh solvent, monomer and catalyst material.

2. A method according to claim 1 comprising the step of modifying the change in said polymerization or copolymerization conditions with time to produce different products at said terminal point, further comprising the step of mixing said different products.

3. A method according to claim 1 comprising the step of maintaining the velocity of said separators and batches substantially constant at each point along said tubular reactor between said point of origin and said terminal point.

4. A method according to claim 1 comprising the step of maintaining the velocity of said separators and batches within the range of one to ten times the interior diameter of said tubular reactor per second at each point along said tubular reactor between said point of origin and said terminal point.

5. A method according to claim 1 comprising the step of spacing said separators apart a. distance equal to ten to two hundred times the interior diameter of said tubular reactor.

References Cited UNITED STATES PATENTS 3,057,702 10/1962 Pierce et a1 260-X 3,220,998 11/1965 Berger 26094.3 3,297,793 1/1967 Dollinger 260-95X 3,306,889 2/1967 Schappert 26094.9 3,335,111 8/1967 Pray et a1. 260-95X 3,148,037 9/1964 SZego 23-288 3,392,213 7/1968 Berger 260-878 a JOSEPH L. SCHOFER, Primary Examiner W. F. HAMROCK, Assistant Examiner US. Cl. X.R. 

